Other cells that may be assayed by this method if they express TAT188 (either endogenously or after transfection with nucleic acid encoding TAT188) include without limitation SKBR-3, BT474, MCF7 or MDA-MB-468 demonstrating that reduction in E16 expression in breast cancer cells results in cell killing and that breast cancer, as well as prostate, colorectal and other types of cancer, are desirable